Along with the demand for pattern miniaturization of a semiconductor device, there is a variety of stringent requirements with respect to a process such as a film forming process, an etching process or the like. A double patterning process known as one of pattern miniaturization processes is taken as an example. In this process, a thin film is first formed on a pattern of a silicon oxide film. Films called sidewalls are formed by etching on both sidewalls of a concave portion that constitutes the pattern of the silicon oxide film. Subsequently, a hard mask is formed by etching a base film using the sidewalls remaining after removing a resist as a mask pattern.
In order to improve the quality of a pattern generated by sidewalls, it is necessary to match the in-plane uniformity of a thickness of a thin film and the etching characteristic of an etching apparatus. The distribution of an etching rate, which is the etching characteristic, is formed in a concentric shape so that, for example, the etching rate is high in a central portion of a substrate and low in a peripheral edge portion thereof. Thus, a concentric film thickness distribution is required even in a film forming process.
There is well-known a method in which a film forming gas is supplied from above a substrate using a shower head of a film forming apparatus. In this method, there may be a case where a singular point, at which coverage or a film quality is different, appears just below the holes of the shower head. For example, when a concentric thin film is formed by rotating a semiconductor wafer (hereinafter referred to as a “wafer”) which is a substrate to be processed, there is a problem in that a circular defective portion is formed in the wafer due to the singular point.
Furthermore, in the related art, a change in an apparatus configuration such as a change in a process container structure of a film forming apparatus or the like has been performed in order to obtain a concentric film thickness distribution. However, the proper concentric film thickness distribution available after a film formation varies depending on the film quality or process of substrate processing. For that reason, in the case where the concentric film thickness distribution is adjusted by changing the apparatus configuration, it is necessary to optimize hardware for every film quality or process. This leads to an increase in the time or cost required in optimizing the hardware.
In the related art, there is known a technique in which the thickness of a film formed on a wafer is made uniform by disposing a plurality of gas injection parts in a width direction with respect to a film forming gas supply direction, changing a velocity of a gas flow in the width direction with respect to the film forming gas supply direction and rotating the wafer. However, if a film is formed by supplying a film forming gas from a lateral side, there is a problem in that a gas flow is not stabilized at a downstream side and a film thickness is not uniform.
Furthermore, in the related art, there is known a technique in which a concentric film thickness distribution is obtained by adjusting a gradient of a film thickness distribution in a radial direction when a wafer is not rotated, and rotating the wafer. However, this technique cannot solve the problems addressed in the present disclosure.